Maratus robinsoni

A male peacock spider (Maratus robinsoni) exhibits the iridescent scales that he flashes at females during courtship. B.-K. Hsiung et al./Nat. Commun./CC BY 4.0

Optics and photonics

How peacock spiders shimmer and shine with rainbows

The secret is in the scales.

Diminutive spiders sparkle with every colour of the rainbow, thanks to scales shaped like aeroplane wings.

The males of two species of Australian peacock spider, Maratus robinsoni and Maratus chrysomelas, seduce potential mates by waving their abdomens, which shimmer with rich colours. To identify the source of this iridescence, Bor-Kai Hsiung at the University of Akron in Ohio and his colleagues examined the 40-micrometre-long scales that cover the spiders’ abdomens.

The team found that parallel ridges on the surface of each scale reflect visible light and break it into its constituent colours. The scales’ tapered, streamlined shape allows light to bounce off more ridges than if the scales were flat, and separates out subtly different hues. The spiders’ scales could inspire designs for compact, high-resolution spectrometers, the authors say.